Presently, water washdown is the mode used to effect clean-up of chemical spills and of chemical warfare agents which contaminate exterior surfaces. Where non-persistent agents are involved such a washdown, with additional subsequent evaporation and degradation by natural processes (such as interaction with the environment, heat and surfaces) will, with time, clear the area of contamination. However, where persistent agents, enclosed areas, (especially those that house sensitive electronic equipment) and/or contaminated personnel are involved, specialized decontamination methods and materials must be employed.
Examples of standard chemical decontaminants for toxic substances are compositions containing diethylenetriamine, supertropical bleach (STB) and phenolic solutions, such as sodium phenolate. In addition to the foregoing, other substances such as ammonia, sodium hydroxide, sodium carbonate, lime, sodium hypochlorite and trisodium phosphate may be used as decontaminating agents. Heat, soapy water, Fullers' earth and steam may also be used as decontaminants in certain situations.
The use of compositions containing chlorinating agents as decontaminating agents (i.e., supertropical bleach, sodium hypochlorite, etc.) have a number of drawbacks. First, they are extremely corrosive. In addition, they are a potent irritant. Also, and perhaps most importantly, there is a significant vapor hazard associated with the chlorine generated by such agents. Indeed, exceeding the maximum permissible concentration of 3 mg./m.sup.3, or 1.5 mg./m.sup.3 of chlorine as a gas at standard temperature and pressure for fifteen minutes, can result in severe respiratory tract damage. Consequently, when chlorinating agents are employed in either enclosed areas or on personnel, the use of gas masks, special protective gear and the presence of adequate ventilation is required.
Disadvantages associated with the use of compositions containing diethylenetriamine are that, although they react with both the nerve agents and blister agents present in many chemical contaminants thereby effectively removing the hazards presented by the contaminant, within approximately five minutes, personnel performing the decontamination must be masked because of its own vapor generated and rubber gloves must be worn to protect the hands. Thus, it is unsuitable for decontaminating personnel. In addition, diethylenetriamine is partially corrosive, is an effective paint remover, and is combustible, resulting in fires when brought in contact with supertropical bleach (STB). Accordingly, its very properties preclude its use in enclosed areas especially when sensitive electronic equipment is housed therein.
For the effective decontamination of clothing, hard surfaces and sensitive electronic equipment, it is necessary to solubilize, disperse and homogenize deposits of the contaminating agent in order to provide rapid and intimate contact with the chemical decontaminating reagents. The possible use of thickened contaminating agents and the penetration of the contaminating agents in grease, oil, soils and porous surfaces require that the decontaminating system have detergents, dispersants and a means of physically brushing the decontaminating reagents onto the surface to be treated. In the decontamination of equipment that is sensitive to corrosion, non-corrosive decontaminants must be employed. Also, the toxicity of the decontaminating reagents must be of a low order in cases where it is to be applied to clothing and directly to contaminated personnel.
In the use of any reliable decontaminating system and procedure, one must assume that the worst set of circumstances possible exist. For example, a contaminating agent which, based of its volatility, is classified as non-persistent, may become persistent by virtue of several occurrences such as its dissolution in water or by its incorporation into films, soils and thickening agents. Thus, it must always be assumed that the contaminant involved has, if possible, become persistent and "clean up" thereof must proceed accordingly.
Assuming that an effective chemical decontaminating agent is employed, it is also necessary that the reactants, (i.e., contaminating agent and decontaminant) be brought together in intimate and homogeneous contact with one another. Otherwise, such as is the case where mustard gas is involved, a shell forms around the mustard globule preventing the decontaminent from further reacting therewith. Accordingly, a system which prevents formation of such globules and provides this effective solubilization and homogeneous contact is required.
A means is also required for effectively and safely dispensing and applying the decontaminating chemicals by relatively untrained personnel who may also become contaminated by contact therewith. Further, the decontaminating system must not impose a logistical burden, but rather, it must be able to rapidly deployed and must be readily available for use without requiring excessive manipulation.
Ideally, the decontaminating system must also be thermally stable, efficacious, noncorrosive and operable at temperature extremes. Moreover, the system should not present any hazards to the user and the environment.